Internal combustion engines with exhaust gas recirculation (EGR), especially compression ignition engines, typically employ EGR coolers. EGR coolers are heat exchangers that typically use engine coolant to cool exhaust gas being recirculated into an intake system of the engine. Engine exhaust gas typically includes combustion by-products, such as unburned fuel, many types of hydrocarbon compounds, sulfur compounds, water, and so forth.
One of the drawbacks associated with the exhaust gas recirculation is fouling of the EGR cooler over a period of time of operation. The fouling layer typically includes carbon particles from incomplete combustion as well as unburned hydrocarbons, sulfuric acid compounds, and minerals such as oil ash. These substances agglomerate on the cooled surfaces of the EGR cooler driven by thermophoresis, condensation, and other mechanisms. The substances adhere to the surfaces of the EGR cooler by adhesive and cohesive forces, Van der Waals forces, and condensation. Fouling of the EGR cooler poses a significant challenge as the fouling layer increases the pressure loss in the heat exchanger and reduces the heat transfer rate, both of which adversely affect the engine efficiency, performance, and emissions.
Conventionally, anti-fouling features are incorporated in the EGR cooler, and the size of EGR cooler is increased to mitigate drawbacks associated with the fouling of the EGR cooler. However, such a conventional EGR cooler would need larger and more expensive area and volume and may also result in even faster formation of the fouling layer in the EGR.
For these and other reasons, there is a need for embodiments of the invention.